From 4b954c347a189dd61eb5ddb98f502f525c749a95 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Steven=20Sch=C3=A4fer?= <stevenschaefer@google.com>
Date: Thu, 13 Feb 2020 14:45:49 +0100
Subject: [PATCH] JVM IR: Avoid optimizing comparisons between boxed primitives
 and null

A comparison of the form `x == null` where `x` is of type `Int` might not
be vacuous if `x` is a boxed value coming from Java code.
---
 .../jvm/lower/JvmOptimizationLowering.kt      | 25 +------------------
 .../unsafeNullCheckWithPrimitive.kt           |  3 ---
 2 files changed, 1 insertion(+), 27 deletions(-)

diff --git a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmOptimizationLowering.kt b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmOptimizationLowering.kt
index f8d7f4aa9ed..6419a705e56 100644
--- a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmOptimizationLowering.kt
+++ b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmOptimizationLowering.kt
@@ -10,7 +10,6 @@ import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
 import org.jetbrains.kotlin.backend.common.lower.irBlock
 import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
 import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
-import org.jetbrains.kotlin.backend.jvm.lower.inlineclasses.unboxInlineClass
 import org.jetbrains.kotlin.codegen.intrinsics.Not
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.ir.IrStatement
@@ -24,7 +23,6 @@ import org.jetbrains.kotlin.ir.expressions.impl.IrConstImpl
 import org.jetbrains.kotlin.ir.types.isBoolean
 import org.jetbrains.kotlin.ir.types.isNullableAny
 import org.jetbrains.kotlin.ir.types.isPrimitiveType
-import org.jetbrains.kotlin.ir.types.toKotlinType
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 
@@ -110,33 +108,12 @@ class JvmOptimizationLowering(val context: JvmBackendContext) : FileLoweringPass
                 }
 
                 getOperandsIfCallToEqeqOrEquals(expression)?.let { (left, right) ->
-                    val constFalse =
-                        IrConstImpl.constFalse(expression.startOffset, expression.endOffset, context.irBuiltIns.booleanType)
-
                     return when {
                         left.isNullConst() && right.isNullConst() ->
                             IrConstImpl.constTrue(expression.startOffset, expression.endOffset, context.irBuiltIns.booleanType)
 
                         left.isNullConst() && right is IrConst<*> || right.isNullConst() && left is IrConst<*> ->
-                            constFalse
-
-                        right.isNullConst() && left.type.unboxInlineClass().isPrimitiveType() ||
-                                left.isNullConst() && right.type.unboxInlineClass().isPrimitiveType() -> {
-                            val nonNullArgument = if (left.isNullConst()) right else left
-                            if (hasNoSideEffectsForNullCompare(nonNullArgument)) {
-                                constFalse
-                            } else {
-                                IrBlockImpl(expression.startOffset, expression.endOffset, expression.type, expression.origin).apply {
-                                    statements.add(
-                                        nonNullArgument.coerceToUnitIfNeeded(
-                                            nonNullArgument.type.toKotlinType(),
-                                            context.irBuiltIns
-                                        )
-                                    )
-                                    statements.add(constFalse)
-                                }
-                            }
-                        }
+                            IrConstImpl.constFalse(expression.startOffset, expression.endOffset, context.irBuiltIns.booleanType)
 
                         else -> expression
                     }
diff --git a/compiler/testData/codegen/box/platformTypes/unsafeNullCheckWithPrimitive.kt b/compiler/testData/codegen/box/platformTypes/unsafeNullCheckWithPrimitive.kt
index 5ae07aadc28..1da594894f9 100644
--- a/compiler/testData/codegen/box/platformTypes/unsafeNullCheckWithPrimitive.kt
+++ b/compiler/testData/codegen/box/platformTypes/unsafeNullCheckWithPrimitive.kt
@@ -1,6 +1,5 @@
 // IGNORE_BACKEND_FIR: JVM_IR
 // TARGET_BACKEND: JVM
-// IGNORE_BACKEND: JVM_IR
 // FILE: Unsound.java
 
 import test.Wrap;
@@ -17,6 +16,4 @@ package test
 
 class Wrap<T>(val x: T)
 
-// JVM IR generates bytecode that fails with NPE because it unwraps the value with `Number.intValue()`,
-// whereas JVM generates a simple null check without unwrapping the box.
 fun box(): String = if ((Unsound.get<Int>() as Wrap<Int>).x == null) "OK" else "Fail"